嗜水气单胞菌J-1株OmpA融合蛋白的高效表达及免疫原性分析

以嗜水气单胞菌（Aeromonas hydrophila）J-1株基因组为模板,根据GenBank已发表的嗜水气单胞菌外膜蛋白的基因序列设计1对引物,扩增去除信号肽序列的成熟外膜蛋白OmpA的基因片段,定向克隆至表达质粒pET32a（＋）中,重组质粒经限制性酶切鉴定后测序。结果表明,插入片段长度为948bp,与NCBI上登录的几个相关序列相比,同源性在93．1％-95％之间,缺失4个氨基酸。将重组原核表达质粒pET32a-OmpA转化至大肠杆菌BL21（DE3）,经诱导可表达分子量约57．4kD的蛋白,凝胶薄层扫描显示OmpA在转化菌中表达量占全菌蛋白的50％以上。用兔抗J-1株总外膜蛋白血清进行Western blot,在57．4kD处有明显反应条带。融合蛋白经Ni-NTA树脂柱亲和层析纯化后免疫新西兰兔制备抗血清,ELISA效价达1：12800以上。Western blot检测结果显示,该血清与9株具有代表性的气单胞菌的分子量约35kD的外膜蛋白均有较强反应,说明所表达的融合蛋白不仅保持原有外膜蛋白的免疫原性,而且提示OmpA可能是嗜水气单胞菌的共同保护性抗原。[中国水产科学,2008,15（2）：301—306]     

Effects of Dietary Binders on Survival and Growth Performance of Postlarval Tongue Sole, Cynoglossus semilaevis (Günther)

A 30‐d feeding experiment was conducted in tanks to investigate the effects of four different binders (2% in microdiet) on the survival, growth performance, and specific activity of digestive enzymes in tongue sole, Cynoglossus semilaevis Günther, postlarvae (24 d after hatching, with initial average wet weight of 22.4 ± 6.65 mg [mean ± SD]). Five approximately isonitrogenous and isoenergetic microbound diets were formulated with carrageenan (Car), sodium carboxymethylcellulose (CMS), sodium alginate (SA), and gelatin (Gel) as binders, and a diet with no special binder as a control. A commercial diet (RQ Com., manufactured by Marubeni Nisshin Feed Co., Ltd., Chita, Japan) was used as another tested diet, and Artemia nauplii was used as live prey control. The results showed that the survival of the fish fed SA diet (31.3%) was significantly higher than that of fish fed CMS (21.8%), Car (10.8%), and control (21.8%) diets (P < 0.05), but significantly lower than that of the fish fed the live prey (54.5%) diet (P < 0.05). The results of growth followed the similar pattern as that of survival, although there were no significant differences in specific growth rate (SGR) among fish fed SA, CMS, Gel, the control, and RQ diets (7.2, 6.8, 7.0, 6.9, and 7.3% per day; P > 0.05). However, fish fed Car diet had a significantly lower SGR (5.9% per day) than fish fed other diets. Percentages of secreted amylase in fish fed artificial diets were not significantly different, but fish fed artificial diets had significantly higher (P < 0.05) secreted amylase than live prey group. Percentage of secreted trypsin in fish fed SA diet (54.9%) was relatively higher compared with other binders, and not significantly different from RQ Com. and live prey treatments. However, trypsin in fish fed Car diets (29.3%) was significantly lower than in other groups. Specific activities of alkaline phosphatase (AP) in the intestine and AP and leucine aminopeptidase N in brush border membranes in fish fed SA diet (264.6, 1882.8, and 187.2 mU/mg protein) were relatively higher compared with other binders. These results indicate that SA is one of suitable binders compared with carrageenan, CMS, and gelatin in microdiet of postlarval tongue sole.     

Immune Responses and Resistance against Vibrio parahaemolyticus Induced by Probiotic Bacterium Arthrobacter XE-7 in Pacific White Shrimp, Litopenaeus vannamei

A 63-d feeding experiment was conducted to determine the effects of dietary supplementation of probiotic bacterium Arthrobacter XE-7 on immune responses and resistance against Vibrio parahaemolyticus in the Pacific white shrimp, Litopenaeus vannamei . The probiotic bacteria were administered orally at four different doses of 0, 10⁶, 10⁸, and 10¹⁰ colony-forming unit (CFU)/g feed for shrimp. On Day 50, the shrimp were challenged with Vibrio parahaemolyticus by bath. On Days 7, 21, 49, and 63, six shrimp per tank were sampled to take intestine and hemolymph. With increasing dietary supplementation of probiotic bacteria, shrimp mortality decreased from 63.16% (the control) to 55.9% (10⁶ CFU/g feed), 51.75% (10⁸ CFU/g feed), and 51.78% (10¹⁰ CFU/g feed), respectively. Vibrio counts in intestine of shrimp fed probiotic bacterium Arthrobacter XE-7 was generally lower than that in the control shrimp ( P  < 0.05). The probiotic bacteria generally increased the immune parameters in shrimp, that is, total hemocyte counts, percentage phagocytosis, respiratory burst activity, and serum phenoloxidase activity. The results showed that probiotic bacterium Arthrobacter XE-7 can be used as probiotic in shrimp feed.     

中美渔业全方位合作的商机

本文全面介绍了中美企业在养殖业、水产贸易与来料加工等领域的广泛合作,表明在中国渔业现代化和养殖生态化进程中,美商看好中国市场。在另一方面,我国水产品多数属低端产品,以后水产品将向高附加值食品方向发展,美国将进口更多的中国水产食品。     

采用施奈德重合器实现馈线自动化的实践研究

针对基于传统重合器的馈线自动化原理及存在问题,提出基于施奈德重合器的馈线自动化方案。以大连庄河炮台变电所石山线-龙王庙变电所水泥线为例,分析施奈德重合器的馈线自动化工作原理,指出该馈线自动化系统在实践中的优点和不足。     

灌溉水矿化度及盐分带入量对小麦相对产量影响的统计分析

在搜集、统计大量咸水灌溉试验资料的基础上,选取咸水充分灌溉条件下矿化度和小麦产量的完整对应数据103组,统计分析了灌溉水矿化度及单位面积盐分带入量对小麦相对产量的影响,结果表明,随着灌溉水矿化度的增加,小麦相对产量呈线性递减趋势,当矿化度大于1.0 g/L时,灌溉水矿化度每增加1 g/L,小麦减产约5.6%;与矿化度类似,随着单位面积盐分带入量的增加,小麦的相对产量也线性降低,盐分带入量每增加1000 kg/hm2,小麦的产量将减少约2%。进一步的检验结果显示,应用灌溉水矿化度及单位面积盐分带入量均可较为可靠地估算小麦的相对产量,估算相对误差基本可控制在16%以内。     

基于土壤墒情模拟的农业干旱动态评估

已有的农业干旱研究中,土壤墒情的模拟与干旱程度的动态评估常常是独立进行的,二者并没有统一起来。基于此,建立了田间土壤水分平衡模型,通过作物生育期内的土壤水分模拟农业干旱过程。为了将土壤墒情模拟与农业干旱的动态评估统一起来,引入了阶段性的作物水分生产函数,通过干旱缺水对农业产量影响的定量分析,反推得出作物不同生育阶段土壤水分状况对应的干旱程度和缺水权重,从而将土壤墒情模拟与农业干旱评估结合起来,达到农业干旱动态模拟与评估的目的,为从土壤墒情状况实时动态评估农业干旱程度提供了一种便捷可行的方法。最后将提出的模型方法结合某灌区进行了应用,效果较好。     

现代汽车电控巡航系统控制原理浅谈

介绍了巡航电控技术的作用、特点、类型、控制原理,其中着重介绍巡航电控系统两种执行器的控制原理.     

汽车悬架阻尼匹配研究及减振器设计

为了使车辆满足平顺性要求,对车辆悬架系统阻尼匹配进行了研究,建立了最佳阻尼比设计方法及减振器速度特性分段线性数学模型.以此模型为基础,建立了减振器阎系参数设计数学模型,并对阀系参数进行优化设计.对设计减振器进行了特性试验和整车振动试验,并与原车裁减振器性能进行了对比.结果表明,车辆悬架系统阻尼匹配合理,减振器阀系参数设计方法正确,设计参数值准确、可靠.     

中小功率内燃机空气滤清器的应用现状

综述了与空气滤清器研究有关的文献,主要包括空气滤清器的原理,研究现状及发展趋势,并在此基础上提出未来一些课题的可能研究方向.